Add splitIndex Javadoc option to the root project
Add splitIndex Javadoc option to the root project

Splits the very large index page with all classes into individual pages
organized by first letter.

Issue: SPR-4984

spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework